At around 3pm Sunday, the man drove a 5.5-tonne light-duty truck to On Muk Street in Shek Mun.
When he opened the door of the truck, the suspects rushed towards him. Two of them caught the man, while the remaining one stabbed him with a sharp weapon.
The three attackers fled in a private car afterwards.
The man's right foot was stabbed many times, and the injuries were to the bone. He was taken to Prince of Wales Hospital and is currently in intensive care.
The police tried to intercept the suspects after receiving the report from a passerby but found nothing.
It is understood that the victim was working for a waste oil recycling company but set up his own business recently.
The police are investigating if the attack was caused by a business dispute. Further investigation is necessary to find out the reason for the assault.
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